An interactive blog of the Florida Renewable Energy Association

Archive for January, 2010

I can still remember thirty years ago when I learned about the first solar thermal electric plants out in California. What a beautiful concept! Build a ring of mirrors so that when sunshine reflects off them the photons will strike a central boiler and create steam to drive a turbine. That, to me, was simplicity and beauty! Never mind turning the earth inside out graveling for coal and uranium. The sun was giving away photons without even asking transportation costs.

Now, the levelized economics and the requirements for environmental / atmospheric safety (RPS) have created new concentrating solar power (CSP) plants out west with applications submitted for more. Florida Power and Light will soon have its own hybrid CSP / natural gas plant operating right here in this state.

Designs for these plants have improved into the second and third generations. But one thing remains the same. Just like fossil and nuclear powered plants, they require water for cooling. To give you an idea, a CSP plant consumes about 800 gallons per megawatt-hour. A typical nuclear plant consumes about 600 gallons per megawatt-hour. Thirty years ago, fresh water was not a resource thought to be close to depletion. Now, we’re not so sure.

Carey King and Michael Webber discuss water vs. energy in their article in the Jan-Feb Solar Today Magazine. Water is not only necessary for life on earth, it’s necessary for the energy we’ve been using. Water availability must now be part of the decision-making when new power plants are permitted. Permits for more CSP plants where they are popular in California may be held up due to water shortages. Deserts are ideal for sunlight but not for water.

The writers say much research is going now into dry and hybrid cooling towers for CSP plants and that water requirements can be brought down to 100 gallons per megawatt-hour. Presently, these water saving methods reduce efficiency and cost more.

Of course photovoltaics, except to wash off dust and bird droppings, require no water at all while producing electricity and neither do solar-convection-driven wind turbines. The amazing solar sterling engines use a miniscule 10 gallons of water per megawatt-hour and their conversion efficiencies are as high as 25 percent. Read about them here. It’s hard to challenge the efficiency and water-conserving attributes of distributed generation; PV on rooftops and in backyards, delivering electricity close to the end user.

Fresh water from desalination requires lots of power. We can use sunlight for that, too. CSP can provide the thermoelectricity to power desalination plants. Australia is using wind generated electricity for desalination now. And finally, higher grade solar heated water can provide the heat for carbon dioxide capture systems at coal power plants. Yes, we can even sequester the residues from old fossils by using our most fundamental energy source, the sun.

Sam kendall

SOLAR TODAY Jan-Feb 2010, Water vs. Energy: How Solar Power Can Help, by Carey W. King and Michael E. Webber

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The Southwest Florida Regional Planning Council (SWFRPC) and St. Lucie County have taken action to resolve the barrier of up front costs in order to get solar panels on more rooftops. Businesses and residents in these areas may soon be able to get solar installed and have the whole cost spread out over time. SWFRPC has made an application for American Recovery and Reinvestment Act grant money to get their program started and St. Lucie County has applied for a grant from the US Department of Energy. Decisions should be known by March of this year. If approved, participants in Charlotte, Glades, Collier, Hendry, Lee and Sarasota counties could get solar installed for combined solar assessments and utility payments that would not exceed their current utility bills. When the systems are paid off they will only pay the lower utility bill. St. Lucie county participants would have access to low-interest solar loans. These residents would also enjoy lower utility bills. Congratulations to the St. Lucie Commissioners and the staff at SWFRPC for involving local government in the clean energy transition.